This invention relates to hand stamps and more particularly to a self-inking hand stamp that does not require an external stamp pad.
The prior art consists of many conventional stamps that require manufacturing the printing surface from rubber or other flexible material. The printing surface is securely mounted on a handle that is grasped by the user. The printing surface is placed into contact with an inkpad where ink transfers to the printing surface. The inked printing surface is then pressed against the surface onto which the stamp image is to be transferred. Repetition of the stamping process requires that the printing surface be pressed against the inkpad each time an image is to be transferred. This is a disadvantage to the user as it requires extra time for each re-inking step and slows down the stamping process if multiple stampings are to be done. It also requires the use of a separate inkpad that must be periodically re-inked.
An improved stamp was developed that uses a printing surface made from an ink permeable material that allows ink to pass from an ink storage member, through the printing surface and onto the object being marked. This eliminated the need for a separate stamp inkpad. These stamps are referred to as self-inking or pre-inked hand stamps. There is no simpler stamping device to transfer images than the pre-inked hand stamp.
An example of this stamp is illustrated in U.S. Pat. No. 5,577,444 issued to Toyama. This patent illustrates a hand stamp that has a sealed ink compartment that stores the ink. The ink can be refilled into the compartment by means of removing a threaded screw at the top of the compartment. Once the screw is removed, the ink can be injected, and the screw replaced. The stamping member has a stamping surface with stamping and non-stamping portions. The stamp pad is fixed to the stamp frame at the factory and is not designed to be field installed or removed.
There are several problems with this device. First, the porous foam or printing surface is factory sealed. If an error is made during manufacturing, the entire mount must be thrown away, thus increasing costs. Since it is factory sealed, a special machine is required to expose the porous foam to form the image on the porous foam surface.
Another type of stamp is illustrated in U.S. Pat. No. 5,942,312 issued to Venkataraman et al. This patent discloses a pre-inked thermoplastic foam which has open cells in the area that is designed to transfer ink and closed or sealed cells in the area which is designed to be impermeable to ink. The pre-inked thermoplastic foam is pre-inked before the image is formed on the thermoplastic material. Thus, if there is a problem with the image, the entire pad including the ink, is wasted. Furthermore, there may be difficulties in forming an image on a pre-inked thermoplastic foam as it may be messy or require special handling due to the ink in the pre-inked thermoplastic foam. The pre-inked thermoplastic foam is mechanically held to the stamp and assembled at the factory. The pre-inked thermoplastic foam is not designed to be installed or removed in the field.
A problem not solved by the prior art devices is providing a die box, also called a stamp frame, that holds the ink supply and printing member, in a single unit, which is easily removed from the hand stamp for re-inking or replacement.
Applicant's invention addresses and solves the problems of the prior art devices. The invention comprises a hand stamp that utilizes a porous foam layer, which is also an ink storage layer mounted in a die box within the hand stamp. The porous foam layer has the image forming stamp material on its outside surface. The image forming stamp material is a porous foam material and has an outer surface made of a porous resin layer. To form the printable image, portions of the porous resin layer are melted and solidify into impermeable areas that are ink impermeable, and other portions of the porous resin layer remain unmelted and allow ink to pass. The releasable die box is uniquely mounted in the stamp by means of releasable locking tabs. A dust cover at the bottom of the stamp snaps into place to cover the bottom of the stamp when in a stored position. The cover can be reversed to hold the stamp in an easily removed resting position when the user is in the process of stamping multiple pieces of material.